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r,OK.\CKTIC ACID

liquid is thereby transferred to the second receiver b; c is now
closed, c is opened and tf turned so as to let: air into b ; b may
now be removed and replaced by a similar vessel and the pro-
cess repealed. Fig. 60 needs little explanation. There are two
or more receivers on one stem. P>y rotating the stem the dis-
tillate falls into one or other receiver. Fig. 61 consists of a
vacuum vessel containing a series of test-tubes which can be
moved in turn, under the end of the condenser, by means of a
vertical axis. It is often preferable to beat the distilling" flask
in an oil or metal bath instead of using wire-gauze. Distilling
flasks above 250 c.c. capacity should not be used for low pres-
sures, as they may collapse. For high boiling liquids, or for
substances which may solidify in the condenser, a condenser
tube without water-jacket is used. A convenient form of con-
denser tube is shown at <i, Fig. 56. It consists of straight tube
fused on to a short narrower tail-piece. In certain cases it is
found convenient to insert the side-tube of the distilling flask
directly into the neck of the. receiver (see p. 94).
PRKPARATION 17.
Monochloracetic Acid, CH.jCI.CO.OH.
    R. Hofmann, Anna/en, 1857,102, i ; Auger, Behal, Bull. Soc.
Chim,, 1889, (3)2, 145-
roo c.c. glacial acetic acid.
10 grins, sulphur (flowers).
Fit up the apparatus shown in Fig. 62.* It consists of a stone-
ware jar one-third full of pyrolusitc in lumps, and fitted with exit
tube and tap-funnel. It is heated on a sand-bath over a small
flame, whilst concentrated hydrochloric acid is allowed to drop
in from the tap-funnel. A rapid current of chlorine is thus
evolved, which is dried by passing through concentrated sul-
phuric acid in the Woulff bottle. The Woulff bottle has a safety
and exit tube, the latter being connected with a straight tube
passing to the bottom of the retort. The retort is tilted upwards
and connected with an upright: condenser, which is furnished
with an open calcium chloride tube. The. acetic acid and sul-
phur are placed in the retort, and heated on the water-bath.
The retort and contents are weighed at the commencement of
the operation on a rough balance. A, rapid current of chlorine